Although many variations of high speed recording tape guides, including air guides, are known and used in the magnetic recording industry, it has been found that a number of serious problems relating to friction and tape alignment have been associated with their use. These problems become particularly acute when processing video signals due to the high tape speeds involved and, consequently, the multiplicity of tracks of extremely narrow width that must be utilized in order to provide record and/or playback capability for programs of reasonable duration on a tape of manageable length.
For example, in a video system which operates at a tape speed of 120 inches per second, 36,000 feet of tape pass the transducing head each hour. Due to physical and cost limitations in reel size, the data is generally recorded on a multiplicity of parallel tracks, and the shorter length of tape which results is passed repeatedly past the transducer head, each time reading information from a different track. In this manner an 1800 foot reel of tape having 30 tracks can be used to record or playback a 90 minute program utilizing the above-described system.
However, the requirement that the tape pass through the transport 30 times per program has resulted in serious wear considerations which it has been found may be greatly overcome through utilization of an air guide type of tape transport. Such prior guides utilizing a film of air as a lubricant have had serious disadvantages associated therewith such as unequal air pressure distribution across the width of the tape which resulted in undesirable deformation of the tape and the requirement for relatively large quantities of air flow under high pressure in order to support the guided span of tape. These problems were eliminated by the air guide designed in accordance with the invention disclosed in my prior U.S. Pat. No. 3,979,037, the disclosure of which is incorporated herein by reference.
Likewise, due to the requirement that 30 different informational tracks be placed in parallel relation on a tape of reasonable and economical width for consumer use, typically 1/4 inch, a related problem concerning alignment of the extremely narrow tracks on the tape with a corresponding transducer head has arisen. This problem is compounded by the fact that commercially available magnetic tape is manufactured to width tolerances which approach the individual track width required (typically about 6 mil with 2 mil spacing between tracks) for utilization of 30 tracks on a 1/4 inch tape format. Such alignment problems have been solved by the air guide designed in accordance with the invention disclosed in my prior U.S. Pat. No. 4,071,177, the disclosure of which is also incorporated herein by reference.
Although the above-discussed prior inventions provided acceptable results in many high-speed tape transport systems, it has been found that due to the fact that the tape must come into contact with the tape guide at the tangent points where the tape enters and departs from the air guide so as to provide an adequate air seal, both undesirable amounts of scrape flutter and contamination build-up on the guide surfaces at these points has resulted which degrade the overall performance of the video system.